This present study numerically examines the flow and thermal characteristics of torus-ring, stent and grooved twisted tape inserts embedded in a smooth circular tube with a ternary nanofluid (SiO₂, ZnO and CaO) as working fluid. The numerical study was performed using ANSYS Fluent for flow regime of Reynolds numbers varying from 500 to 2000 and non-uniform wall temperature profile. Influence of nanoparticle concentrations 0.01% to 0.03%, thickness ratios 0.019 and 0.025, and width ratios 0.38 and 0.48 on pressure drop, Nusselt number and thermal performance factor were examined. The flow characteristics with the use of the ternary nanofluid were compared with that of pure water, while the thermohydraulic performance of the enhanced tubes with five turbulators and a stent were compared with that of smooth tube to generate the enhancement performance factor. Simulation data reveal that flow and thermal indicators such as Nusselt number, thermal performance factor, pressure drop, increase with Reynolds number and augmentation in nanoparticle concentration, thickness ratio and width ratio. The thermal performance factor of 1.5 times over pure water was observed in the tube with ternary nanofluid with equal proportion of nanoparticle concentration 0.03%. The width ratio 0.48 and thickness ratio 0.025 yielded the maximum value of the thermal performance factor of about 0.87 and 1.29 times that of smooth tube, respectively. It is also observed that the thermal performance factor is larger than unity for all the geometric parameters considered in this study. This depicts the efficacy of the proposed heat exchanger when considering it from an engineering and economical perspective.